If director/producer Liam Barker had simply assembled a collage of pretty nature footage while laying American mystical folk guitarist Robbie Basho’s coruscating river of music over it for 90 minutes, he would’ve created a superior documentary. Of course, Barker went far beyond that, and his extensive research and revealing interviews with fellow guitarists like Pete Townshend, Glenn Jones, and Max Ochs, Basho’s Sufi friends, and family members result in a moving portrait of a tormented genius. The Baltimore-born guitarist’s fervent cult has steadily grown since his freakish death in 1986, and Voice of the Eagle: The Enigma of Robbie Basho should add even more devotees to his fan base.

Born in 1940, Basho was orphaned as an infant and adopted rather late in his life by the Robinson family. He attended Catholic schools and was an overweight misfit. According to Ochs, Basho thought that if he excelled at guitar, it would make girls like him. “He went for whatever beauty he could find,” Ochs says. “He was a lone explorer.”

Basho began his musical career in the square world of folk music at the University of Maryland, but hearing Indian sitarist Ravi Shankar’s music in 1962 spurred him to search outside of Western forms to forge his own style. Studying under Indian sarod player Ali Akbar Khan further expanded Basho’s sonic approach. He used open tunings and a 12-string acoustic guitar while also assimilating influences from Japanese, Persian, and Native American musics.

Much of Voice of the Eagle focuses on Basho’s struggle to subdue internal demons—which he thought were bedeviling him from past lives—through the sheer power and beauty of his songs. He became a disciple of Sufism Reoriented Avatar Meher Baba and Murshida Ivy Duce, and that involvement rescued Basho from what he called “ego hell.” Basho also had bad experiences with drugs, defining LSD as “karmic cosmetics.” But despite releasing 14 albums bursting with virtuosic, spiritual playing and eccentrically robust singing, Basho never attained the success of fellow US folk guitarists like Takoma Records cofounder John Fahey or Will Ackerman, who issued two Basho LPs on his big independent label, Windham Hill.

One Voice of the Eagle interviewee surmised that, as we are in the age of the demon, Kali Yuga, where humanity is at its furthest point from “god,” Basho “tried to delve deep into the spirit and bring back something higher.” Throughout this film, you witness his intense journey to transcend mental and physical flaws and achieve a seemingly impossible state of purity and spirituality. By the time we see Basho’s battered and taped guitar case at film’s end, you will have dampened many a tissue with tears at the poignancy of Basho’s truncated, frustration-filled life. recommended

Voice of the Eagle plays at the Grand Illusion on Tuesday, August 23.